The invention relates to the field of haematological analysis, and more specifically to the fractionated distribution of a blood sample.
The expression "blood sample" in this case denotes a volume of blood obtained from a blood sample taken from a patient, and contained in an analysis container, which for example can be an open tube, or a tube closed by a stopper. In general the blood in question is whole or full blood, taken with an anticoagulant.
In haematological analysis, it is often necessary to obtain several fractions of the blood of a patient, which are still known as "aliquots", and are destined to be diluted with different reagents in order to obtain different analysis results.
This is the case in particular for globule counters, which count and differentiate white globules.
For practical reasons, it is preferable to take only a single sample of the patient's blood in a tube, then to fractionate this sample into different aliquots, each of which will then be added to a suitable reagent.
For this purpose, fractionating of the blood sample by means of a sample valve is known, according to the teaching, for example, of publication FR 2 622 692 in the name of the applicant.
These sampling valves have the advantage that they operate at high speeds, which makes them particularly advantageous for specific types of analysers.
However, their main disadvantages are that they require volumes of blood which are far greater than the theoretical volumes necessary for the analysis, they have a complex and costly structure, and they additionally need frequent cleaning, which is difficult to carry out.
In the field of biochemistry, it is also known to collect all of a blood serum in a needle, and then to discharge various successive volumes of this sample, for the purpose of different dilutions.
This specific technique is used for a blood serum, in other words blood from which the globules have been removed, and which thus has lower viscosity than whole or full blood.